Typically speaking, free-standing masonry walls are constructed of concrete blocks (or similar material) in running courses. Each course is placed in such a manner so that the vertical joints are staggered from the previous course. Mortar is used as a binding agent between the courses and between the ends of each of the blocks. Conventional concrete blocks typically have one or more voids extending through them in the vertical direction to create vertical columns through the walls. Reinforcing bars are placed in these columns for enclosure within a continuous mortar masses within the columns, in accordance with building code standards. Such columns typically are placed approximately four feet apart along the length of the wall.
Although this type of free-standing masonry wall has been used successfully in residential, commercial and industrial construction, it possesses a considerable number of drawbacks. These include: the necessity of skilled labor for assembly (not handyman friendly), the requirement of mortar as a binding agent between each of the components, the considerable time demanded for construction, the inability to disassemble components and reuse if desired, the incapacity to absorb external pressure changes (such as settling, hydrostatic pressure and seismic disturbances) without significant deterioration to the structural integrity.
Several types of blocks and wall systems have been proposed to overcome some of these deficiencies. Beginning in 1901, U.S. Pat. No. 676,803 to Shaw, disclosed an interlocking block system that employed a combination of tongues and groves along with dovetails to secure each block to the adjacent blocks. This was followed by similar designs in U.S. Pat. Nos. 690,811 to Waller, 748,603 to Henry; 868,838 to Brewington; 1,562,728 to Albrecht; 2,902,853 Loftstrom ; and, French Patent No. 1,293,147. Although the use of interlocking male and female dovetails provide a positive lock and represent a significant improvement over similar tongue and grove construction, all of the dovetails used in this conventional art embody a critical disadvantage in terms of assembly. When these are employed (as in the case of: U.S. Pat. No. 676,803; French Patent No.1,293,147; U.S. Pat. Nos. 748,603; 1,562,728; and, 2,902,853) on the upper and lower surfaces of the block, the female dovetail of each new block must be slid over a number of male dovetails on the lower course into the appropriate position. Given the dimensional inaccuracies of common block material along with the tolerances necessary to slide the new block into place, binding is a frequent occurrence. Despite a long-felt but unresolved need for handyman friendly construction material, this frequent assembly problem, along with the various proprietary components, kept assembly to skilled professionals.
While much of the conventional art, to a certain degree, overcomes some of the difficulties associated with the requirement of mortar, and the inability to disassemble, none provide for the capacity to automatically absorb external pressure changes without significant deterioration in structural integrity.
Attempts to address this particular problem have come in the form of steel reinforcement of some kind. In 1907, U.S. Pat. No. 859,663 to Jackson employed steel post, tension-threaded reinforcement rods in combination with steel frames to produce a very strong wall. The use of steel post, tension-threaded reinforcement rods can also be seen in: U.S. Pat. Nos. 3,378,96 to Larger; 859,663 to Jackson; 4,726,567 to Greenburg; 5,138,808 to Bengtson et al.; and, 5,355,647 to Johnson et al.
Unfortunately, this move to steel reinforcement as a means to counter external pressure meant the loss of many of the gains achieved by much of the conventional art. In short, the characteristics of: mortarless construction and the ability to disassemble components and reuse them were sacrificed for a stronger wall.
Although the addition of steel to bind the wall in a solid mass contributed to it structural integrity by better resisting certain external forces, this is only true in the case of a force applied in one direction against the wall. As in the case of hydrostatic pressure, the force moves only in one direction; from the outside to the inside, slowly and steadily. Seismic disturbances, such as those associate with earthquakes, tend to move the earth in a rapid back and forth motion. A wall bound as a sold mass is unable to accommodate the dynamic back and forth movement. Instead, its rigid composition directly transfers the force to the rest of the building (acting as sort of a lever) weakening the integrity of the entire structure until it finally fails.
Thus, it is desirable to provide a masonry wall system that incorporates the advantages of: unskilled labor for assembly; mortarless construction; the ability to disassemble and reuse; and, the necessary capacity to automatically absorb external pressure changes (particularly seismic disturbances) without significant deterioration of structural integrity. Such a wall system would create a new synergy that would satisfy a long-felt but unresolved need. It would also represent a positive contribution to the masonry industry.